LITTLE ROCK (AP) — The Arkansas Democratic Party asked an outside congressional office to investigate whether U.S. Rep. Tom Cotton illegally solicited contributions for his Senate bid during a radio interview at the U.S. Capitol last month.

The state party sent a complaint to the Office of Congressional Ethics over a Sept. 30 phone interview Cotton gave to talk radio host Hugh Hewitt. During the interview, Cotton said supporters could visit his website to contribute to his bid to unseat Democratic U.S. Sen. Mark Pryor.

Hewitt said during the interview that Cotton was speaking from inside the Capitol, but Cotton’s office later said he was not in the building when he mentioned the website. Hewitt later said he was mistaken in saying Cotton was at the Capitol throughout the interview.

Benton Smith, an attorney for the party, said in the letter that there was substantial reason to believe that Cotton made the fundraising solicitation from inside the building. Smith also writes that even if Cotton was outside the Capitol when he mentioned the campaign site, “he was obliged nonetheless to avoid the impression that he allowed Mr. Hewitt to create.”

Cotton’s campaign on Tuesday dismissed the complaint as a politically driven, personal attack. Cotton and Pryor have been engaged in a heated fight for the Senate race, with both campaigns and outside groups spending heavily on television advertising more than a year before the election.

“The facts have already proven this to be a false accusation, and we’re confident this partisan publicity stunt complaint will be dismissed,” campaign manager Justin Brasell.

A spokeswoman for the Office of Congressional Ethics declined to comment. Anyone can ask the office to review allegations, but submitting a letter does not automatically result in an investigation.

The office can begin a preliminary review if two of its board members find there’s a reasonable basis to believe a violation occurred, and the investigation can continue on to a second phase if three members say there is probable cause to believe a violation occurred, according to the office’s website.

At the end of an investigation’s second phase, the office must recommend that the House Ethics Committee either review the case further or dismiss the case.

Cotton was elected to south Arkansas’ 4th Congressional District in November. Pryor was first elected in 2002 and is seeking a third term.